1. Field of the Invention
The present invention relates to a retrieving system for information filed in a disk-shaped recording medium.
2. Discussion of Related Art
Recently, attention has been given to disk-shaped mediums such as a floppy disk and a hard disk functioning as a magnetic disk and an optical disk. These disk-shaped mediums have such advantages that access time of desirable data to recording positions during the data retrieving operation can be considerably shortened, as compared with that of a tape-shaped recording medium. More specifically, as to the optical disks, since memory capacities thereof are rather great, such optical disks are the best data recording medium in the file systems. For instance, as to a CD (compact disk) employed as the recording medium of music information, the storage capacity of one side thereof amounts to 500 megabytes. When this CD is employed as a recording medium of a file system (will be referred to as a "CD-ROM"), it is possible to file a huge amount of data in a single CD-ROM.
In the file system with employment of this disk-shaped medium, the index information has been provided with each of the data recorded on the disk-shaped medium, and the tables have been set by which the index information corresponds to address information indicative of the recording position for the data corresponding to this index information on the disk-shaped recording medium. For instance, assuming that data recorded on a disk-shaped recording medium is related to personal histories, the index information will correspond to each of individual means.
When desirable data is read out from the disk-shaped recording medium, information (guidance information) for instructing index information corresponding to this data is externally inputted. In the file system, a search is made of the address information corresponding to the inputted guidance information from the above-described tables, and the disk drive apparatus is driven so as to read out the data recorded on the position of this disk-shaped recording medium which is defined by this address information.
In the disk drive apparatus, upon receipt of the address information, such a seeking or search operation is performed whereby the head is transported in a radial direction of the disk-shaped recording medium until it reaches the track containing the recording region on the disk-shaped recording medium designated by this address information, and the desirable data is reproduced from this recording region.
On the other hand, in the conventional file system, since the index information has a relationship with the disk-shaped recording medium with one to one correspondence, after the guidance information corresponding to this data has been inputted, the retrieving operation is commenced. In other words, after the input operation of the guidance information has been accomplished, the verification between this guidance information and the index information at the above-described tables is carried out to determine the address information, and then the disk drive apparatus starts its seeking or searching operation in response to this address information.
As a consequence, even when the input operation of the guidance information has been accomplished, the desirable data cannot be instantaneously obtained, but may be obtained after a predetermined time period has passed. If consideration is made, for instance, of a CD-ROM, the seeking time required from an innermost part thereof to an outermost part thereof becomes 0.6 to 1 second. Accordingly, the seeking or searching time for data which has been recorded on the recording position close to the innermost part of CD-ROM becomes short. However, even if the time required for verifying the guidance information with the index information on the above-described tables may be neglected or disregarded (for instance, 7 to 8 microseconds required for one verification), the desirable data cannot be simultaneously obtained when the input operation of the guidance information is completed. Moreover, the time periods required after the input operation of the guidance information has been completed until the desired data is available, are different from each other, depending upon the data recording positions on the disk-shaped recording medium. As a result, in the case that the retrieving operation for the data positioned at the outermost side of the disk-shaped recording medium is carried out subsequent to the retrieving operation for the data positioned at the innermost side thereof, a user probably feels that such a data retrieving operation for the outermost side takes a longer time period.